/Engine/Source/Runtime/Core/Public/Async/Fundamental/Scheduler.h
Start number of workers where 0 is the system default
void StartWorkers ( uint32 NumForegroundWorkers, uint32 NumBackgroundWorkers, [FThread::EForkable](API\Runtime\Core\HAL\FThread\EForkable) IsForkable, EThreadPriority InWorkerPriority, EThreadPriority InBackgroundPriority, uint64 InWorkerAffinity, uint64 InBackgroundAffinity )